Influence of oxygen on the polymerization of olefins



United States Patent 2,994,691 INFLUENCE OF OXYGEN ON THE POLY- MERIZATION 0F OLEFINS Stephen Gates, Charleston, W. Va., assignor to Union Carbide Corporation, a corporation of New York No Drawing. Filed Dec. 2, 1957, Ser. No. 699,906 8 Claims. (Cl. 260-949) The present invention relates to a process for increasing the rate of polymerization and the yield of polymer produced per unit of catalyst in the polymerization of alphaolefins with certain metalorganic catalysts at low pressures. More specifically, this invention relates to the use of oxygen or an oxygen-containing gas such as air in contact with the reaction medium of the catalyst and an alpha olefin to increase the speed of polymerization and the yield of polymer produced per unit of catalyst.

It is known that the combination of certain compounds of the transition metals of the group lV-B, V-B and VIB of the periodic table, for example the halides, with organometallic compounds or metal hydrides of aluminum or members of group I-A and IIA of the periodic table, when mixed in an inert liquid hydrocarbon diluent form a catalyst complex. The exact nature of this complex is not known, but when an alpha-olefin is brought in contact with the suspension of catalyst in the diluent, polymerization occurs and a resinous product results.

Ordinarily, the catalyst complex is prepared by reacting the transition metal compound and the group I-A, IIA or aluminum compound to form a slurry of the catalyst complex in the inert diluent at room temperature.

In the past it was believed by those skilled in the art that oxygen should be excluded from the polymerization reaction because it would have a deleterious effect on the catalyst. I have now found that when the polymerization is carried on at temperatures above 125 C. that the rate of the reaction and the quantity of polymer produced per unit of catalyst is greatlyenhanced by the presence of oxygen in the reaction medium. The oxygen may be introduced to the reaction medium by mixing with the olefin feed or by a separate feed of oxygen into the catalyst slurry. Of course, oxygen-bearing gases such as air may also be used. The preferred concentration of oxygen in the practice of applicants invention is from less than about 1000 to about 10,000 ppm. by volume based on the olefin feed. However, oxygen is advantageously introduced within the range of less than about 50 ppm. to as much as 20,000 ppm. based on the volume of the olefin feed. The temperature of the reaction may range from 125 C. to 250 C. with 130 to 190 C. being preferred.

The catalyst complex referred to in this application is composed of (1) a halide or oxyhalide or mixture thereof of a transition metal of groups 1VB, VB, and VIB of the periodic table as found on pages 394-395 in the Handbook of Chemistry and Physics, thirty-eighth edition (1956), published by the Chemical Rubber Publishing Co., such as, for example, vanadium, titanium, tungsten, zirconium, hafnium, niobium, tantalum, chromium, or molybdenum halides. A few such compounds are: vanadium tetrachloride. vanadium trichloride, vanadium dichloride, vanadyl trichloride, vanadyl dichloride, titanium tetrachloride, titanium trichloride, titanium dichloride, zirconium tetrachloride, chromium trichloride, chromyl dichloride, titanium tetrafluoride, titanium trilluoride, titanium tetrabromide, titanium tribromide, tungsten telrachoride. and tungsten hex-achloride, and mixtures thereof. Titanium tetrachloride is most advuntau geously employed in this regard.

The second component of the catalyst complex is an organo-metallic compound or metal hydride such as, for example, triisobutyluluminum, trioctylaluminum, tributylaluminum. triethylaluminum, triisopropylaluminum, trigroup of alpha-olefins.

Patented Aug. 1, 1961 dodecylaluminum, triphenylaluminum, diethylaluminun chloride, diisobutylaluminum chloride, dioctylaluminun chloride, didodecyaluminum chloride, various monohy drocarbonaluminum dihydrides, diethylaluminum hydride diisobutylaluminum hydride, dioctylaluminum hydride didodecylaluminum hydride, aluminum hydride, diethyl beryllium, diisobutylberyllium, dioctylberyllium, didc decylberyllium, diphenylberyllium, ethylberyllium chlc ride, isobutylberyllium chloride, octylheryllium chloride beryllium hydride, dodecylberyllium chloride, lithiur hydride, phenyl lithium, naphthyl lithium, isobutyl litt ium, cyclohexyl lithium, dodecyl lithium, diethylzinc, d isobutylzinc, dioctylzinc, didodecylzinc, diphenylzint ethylzinc chloride, isobutylzinc chloride, dicyclopropy zinc chloride, diisobutylmagnesium, dioctylmagnesiun didodecylmagnesium, diphenylmagnesium, isobutylmag nesium chloride, octylmagnesium chloride, magnesiur hydride, and dodecylmagnesiurn chloride. The preferre organo-metallic cocatalysts are the trialkyl aluminur compounds having less than 13 carbon atoms in each alk} chain such as triisohutylalurninum.

The molecular ratio of the trialkylaluminum to van: dium or titanium tetrachloride can vary from about 0. to about 10 or more. The ratio employed is not narrow] critical and may be varied considerably. Thus, the pol merization works as well at higher ratios; however, a prt ferred molar ratio for efiiciency and economic operatic is from about 0.2 to about-2.0 of the organo-metallic con pound to the transition metal compound. The functic of these metallic complexes being that of catalysts or ll itiators, any catalytic amount can be used. Thus, tl concentration of the catalyst complex in the liquid diluei may vary from about 0.1 millimol per liter to or mot millimols of each component per liter of solvent.

The techniques used in combining the catalyst, dime and monomer are well known procedures designed to e elude moisture. The organo-aluminum cocatalyst can I added to the diluent in the reaction vessel prior to tl addition of the metal halide cocatalyst; however, the various components can be added in reverse order als The monomer and oxygen may be introduced and tl vessel then sealed with subsequent stirring of the reactit mix at the desired temperature. The reaction may tht take place under autogenous pressure. Alternatively, tl monomer and oxygen may be introduced continuously the desired temperature and pressure.

Pressure is not critical and is based only on practit' considerations of equipment design. Polymerization c. be conducted at atmospheric, superatmospheric, or su atmospheric pressure in agitator equipped vessels. Th pressures of 0.1 atmosphere to 2000 atmospheres may used. it is preferable to maintain an inert atmosphe over the reaction medium (cg. nitrogen). A grindi medium may also be present in the reaction mixtu (cg. glass heads) for the purpose of tlecimatiug the met halide and continuously renewing exposed surfaces the decimated particulate metal halide to the monoir and oxygen.

The period of time during which the polymerizati reaction is permitted to proceed is not critical. Th periods of as little as 5 minutes or less to 4 hours 0! days can be elfectively employed. The longer the notion period, the more complete the conversion.

The process of this invention is applicable to n lat Both branched and unbranel alphwolelins and mixtures thereof are contemplated the formation of polymers and copolymers by the proc of this invention. A few of the unbrunched olefins ethylene, propylene, l butene, and l-pentene as well l-hexene, l-heptenc, l-octene, I-nonene, l-decene, l-t decene and the like. The unbranehed alphaolefins pr erably employed contain from 2 to 12 carbon atoms.

few of the branched-chain olefins are: 3-methyl-1-butene, 4-methyl-l-pentene, 3-methyl-1-pentene, 3-methyl-l-hexene, 4-methyl-l-hexene, 3,4-dimethyl-l-hexene, 3-ethyl-lpentene, 3-ethyl-1-hexene, 4-ethyl-l-hexene, -ethyl-lhexene, 4-butyl-l-octene, SethyI-l-decene and the like. A few of the copolymers which may be produced are ethylene with propylene, ethylene with l-butene, ethylene with l-pentene, ethylene with l-hexene and the like. it should be noted that the term copolymer as employed herein refers to polymers containing two or more alphaolefin monomers and thus includes terpolymers and the like as well.

The inert liquid hydrocarbon diluent employed may be: (1) any aliphatic hydrocarbon such as heptane, hexane, cyclohexane, and Z-ethylhexane; or (2) any aromatic hydrocarbon such as benzene, toluene, ortho-, metaand paraxylene; also (3) a mixture of hydrocarbons may be used. However, the hydrocarbon diluent must be free of impurities of unsaturated compounds, sulfur-containing compounds and compounds containing active hydrogen such as alcohols, amines and water. The preferred inert diluents are Bayol D (a purified kerosene) and heptane. It is desirable to have at least one percent by weight of monomer in the diluent during polymerization although the concentration may vary from about one to seventy percent or higher.

The following examples are illustrative of the invention.

EXAMPLE 1 A series of polymerizations was carried out by the fol-- lowing procedure:

One thousand milliliters of Bayol D (a purified kerosene) were placed in a two liter resin flask equipped with an air driven paddle stirrer, a thermometer, an inlet tube extending below the surface, and an outlet tube. To this there were added millimols of triisobutylahuninum in a small amount of purified hexane (about 20 ml.) and 20 millimols of titanium tetrachloride, which had also been slurried in a small amount of hexane (about 20 ml.). The mixture was stirred and heated to 150 C. and maintained at that temperature. Ethylene containing a predetermined amount of oxygen was then passed into the solution at the rate of one liter per minute for a period of one hour. Isopnopanol was then added to quench the catalyst in the mixture. The polymer slurry was poured into about a liter of isopropyl alcohol and was stirred for a few minutes. The resin was then filtered off and dried. The results of the polymerization with varying amounts of oxygen is given in Table I.

Table 1 Test No. Feed Yield, Melt g. Index Ethylene containing about 1,200 ppm. 22 5. 4

by volume of Oz. Ethylene containing about 20-50 p.p.m. 10 0.42

by volume of Oz. Ethylene purified by passing it through it 0. 77

alkaline pyrogallol to remove 02. Same as No. 3 14 0.31 Ethylene containing a total of about 3,500 i 44 0.81

p.p.m. by volur of ()1. 1 Ethylene containing a total of about man i in I in p.p.m. by volume of O2. Ethylene contnning a total of about 12,000 I 24 ll) p.p.m. by volume of 02.

1 Melt index is determined by ASlAl Test Method 1) i230 fil'l.

EXAMPLE 2 A ten-gallon, glass-lined autoclave was charged with 915 parts (5 pounds equals l00 parts) of dry, acid-washed heptane and heated to 140 C. under a dry nitrogen atmosphere. To this was added 0.48 part titanium tetra chloride and 0.46 part triisobutylaluminum (Al :Ti:O.93) with agitation. An ethylene mixture containing 1200 ppm. of oxygen (as 0.6% air), by volume of the ethylene, was then added to the autoclave at a rate sufiicient to maintain a reactor pressure of p.s.i.g. The temperature went out of control immediately, reaching almost C. within a few minutes after the beginning of the reaction. Temperature control was restored by throttling the flow of the ethylene mixture. After the first vigorous reaction had subsided, each catalyst component and additional diluent was added in small portions from time to time. Each addition of catalyst caused a marked increase in polymerization rate, and was accompanied by diificulty in maintaining temperature control. At the end of 200 minutes, the reaction was arbitrarily stopped. One hundred parts of ethylene had been passed into the reactor. In addition to the original quantities of catalyst and diluent, an additional 1.66 parts titanium tetrachloride, l.62 parts triisobutylaluminum and 53 parts heptane had been added to the autoclave prior to stopping of the reaction. The contents of the autoclave were poured into isopropanol, and the resin was worked up and recovered in the usual manner. Four and three-tenths pounds of polyethylene having a melt index of 80, and a density of 0.964 were obtained.

EXAMPLE 3 This example was run with a mixture of ethylene and air in the same manner as that of Example 2. At the end of 220 minutes the reaction was arbitrarily stopped. Eighty-five parts of ethylene containing about 1200 ppm of oxygen by volume and a total of 1.23 parts titanium tetrachloride and 1.19 parts of triisobutylaluminum were used to effect the polymerization of 5.5 pounds of polyethylene having a melt index of 210 and a density of 0.965. The polymer was recovered in the same manner as that described in the preceding examples.

EXAMPLE 4 This example was run in the same manner as the preceding two examples, except that the ethylene was substantially free of air and contained no more than about 50 ppm. of 0 by volume, based on the ethylene. Titanium tetrachloride, 5.95 parts, and triisobutylalurninum, 5174 parts, (Al:Ti=0.93), yielded only 2.8 pounds of polyethylene having a density of 0.964 and a melt index of 1.4 in a reaction period of 250 minutes. The reaction had stopped prior to the 250 minutes and the violent reaction observed in the previous two examples did not OCCUI.

The organo-metallic compounds or metal hydrides that may be used with the titanium trichloride are those compounds of groups I-A, ILA, and Ill-A of the periodic table and may be exemplified by formulas such as:

wherein R is a member selected from the group consisting of hydrogen and a monovalent hydrocarbon radical; each of R and R is a member selected from the group consisting of hydrogen and a monovalent hydrocarbon radical and halogen when no hydrogen is directly attached to the metal. in the preferred method R is a member selected from the group consisting of hydrogen, an aromatic hydrocarbon radical contains 6 to I12 carbon atoms, a saturated aliphatic hydrocarbon radical containing two to twelve carbon atoms and a saturated cycloaliphatic hydrocarbon radical containing 3 to 12 carbon atoms; each of R and R is a member selected from the group consisting of hydrogcn, a saturated aliphatic hydrocarbon radical con taining 2 lo l2 carbon atoms, a saturated cycloaliphatic lrvdrocarbon radical containing 3 to l2 carbon atoms, an aromatic hydrocarbon radical containing six to twelve carbon atoms and halogen when no halogen is directly attached to the metal.

What is claimed is:

l. A process for polymerizing an alpha-olefin containing 2 to 12 carbon atoms at a temperature of 130 C. to 190 C. which comprises admixing said alpha-olefin with from 1,000 to 10,000 p.p.m. of molecular oxygen, based on the volume of the alpha-olefin, and subsequently forming a polymer by contacting the mixture of oxygen and alpha-olefin with a catalyst slurry composed of: an inert liquid hydrocarbon diluent; an inorganic halide of a transition metal selected from the group consisting of group lV-B, V-B and Vl-B of the periodic table; and a compound selected from the group consisting of R--ZnR R-Be-,R R-MgR and RLi, wherein Al is aluminum, Mg is magnesium, Zn is zinc, Be is beryllium, Li is lithium. R is a member selected from the group consisting of hydrogen, an aromatic hydrocarbon radical containing six to twelve carbon atoms, a saturated aliphatic hydrocarbon radical containing two to twelve carbon atoms and a saturated cycloaliphatic hydrocarbon radical containing 3 to 12 carbon atoms, each of R and R is a member selected from the group consisting of hydrogen, a saturated aliphatic hydrocarbon radical containing two to twelve carbon atoms, a saturated cycloaliphatic hydrocarbon radical containing 3 to 12 carbon atoms, an aromatic hydrocarbon radical containing 6 to 12 carbon atoms and a halogen when no hydrogen is directly attached to the metal. 7

2. The process of claim 1 wherein the alpha-olefin is ethylene.

3. The process of claim 1 wherein the catalyst slurry is composed of an inert liquid hydrocarbon diluent, titanium tetrachloride and a trialkylaluminum compound containing 2-12 carbon atoms in each alkyl chain.

4. The process for polymerizing ethylene at a temperature of 130 C. to 190 C. which comprises admixing the ethylene with 1000 to 10,000 ppm. of oxygen by volume, based on the volume of ethylene feed, and subsequently progressively passing the mixture into a catalytic amount 5. The process of claim 4 wherein the inert liq hydrocarbon diluent is hexane.

6. The process of claim 4 wherein the inert liq hydrocarbon diluent is heptane.

7. The process of claim 4 wherein the inert liq hydrocarbon diluent is purified kerosene.

8. In the process for polymerizing an alpha-olefin c taining from 2 to 12 carbon atoms by contacting said phaolefin with a catalytic amount of a catalyst complex an inert liquid hydrocarbon diluent wherein the cata complex is composed of: (a) an inorganic halide 0 transition metal selected from the group consiting group IV-B, V-B and VI-B of the periodic table; an compound selected from the group consisting of RZn-R RBeR R-MgR and R-Li, Wht in Al is aluminum, Mg is magnesium, Zn is zinc, B beryllium, Li is lithium, R is a member selected from group consisting of hydrogen, an aromatic hydrocar radical containing six to twelve carbon atoms, a saturz aliphatic hydrocarbon radical containing two to twt carbon atoms and a saturated cycloaliphatic hyd-rocar radical containing 3 to 12 carbon atoms, each of R R is a member selected from the group consisting hydrogen, a saturated aliphatic hydrocarbon radical taining two to twelve carbon atoms, a saturated cy aliphatic hydrocarbon radical containing 3 to 12 car atoms, an aromatic hydrocarbon radical containing 1 12 carbon atoms and a halogen when no hydroge: directly attachedto the metal; the improvement wl comprises conducting the process at a temperature 125 C. to 250 C. while the said alpha-olefin is in con with from 1,000 to 20,000 ppm. of molecular ox; based on the volume of alpha-olefin.

References Cited in the file of this patent UNITED STATES PATENTS 1,140,429 Du Pont M Mar. 4, 1 2,822,357 Brebner et al. Feb. 4, 1 2,827,446 Breslow Mar. 18, 1 2,827,447 Nowlin et al. Mar. 18, 1 2,839,518 Brebner June 17, 1 2,868,771 Ray et al Ian. 13, 1 

1. A PROCESS FOR POLYMERIZING AN ALPHA-OLEFIN CONTAINING 2 TO 12 CARBON ATOMS AT A TEMPERATURE OF 130*C. TO 190*C. WHICH COMPRISES ADMIXING SAID ALPHA-OLEFIN WITH FROM 1,000 TO 10,000 P.P.M. OF MOLECULAR OXYGEN, BASED ON THE VOLUME OF THE ALPHA-OLEFIN, AND SUBSEQUENTLY FORMING A POLYMER BY CONTACTING THE MIXTURE OF OXYGEN AND ALPHA-OLEFIN WITH A CATALYST SLURRY COMPOSED OF: AN INERT LIQUID HYDROCARBON DILUENT, AN INORGANIC HALIDE OF A TRANSITION METAL SELECTED FROM THE GROUP CONSISTING OF GROUP IV-B, V-B AND VI-B OF THE PERIODIC TABLE, AND A COMPOUND SELECTED FROM THE GROUP CONSISTING OF 